Cochlea: cross section (English)

The cochlea is the structure of the internal ear responsible for hearing. Its structure resembles a snail shell situated in the bony labyrinth of the temporal bone. The 'shell' of the cochlea is wrapped 2.75 times around its axis, known as the modiolus. The crosssection of the cochlea reveals its internal structure which is characterized by the cavity of the cochlea (spiral canal) and a triangular membranous duct, called the cochlear duct (also known as the scala media). The scala media is filled with endolymph. In addition to the scala media, there are two more canals that run parallel to one another, the scala vestibuli and scala tympani. In contrast to the scala media, the scala vestibuli and scala tympani are filled with perilymph. Sound vibrations transmitted from the middle ear through the vestibular window result in mechanical movements of the fluids inside the cochlea which moves the basilar membrane. Movements of the basilar membrane in turn cause movements of the structures within the cochlear duct. These movements are converted to electrical impulses in the receptor part of the cochlea known as the spiral organ (of Corti).